An embodiment of the invention generally relates to an audio device that reduces interference caused by active noise cancellation circuitry picked-up by a hearing aid that is electromagnetically coupled to the audio device. Other embodiments are also described.
Ambient acoustic noise is background audio waves that may be heard by a user. Many mobile phones have been equipped with active noise cancellation circuitry to reduce or eliminate the effect ambient acoustic noise has on a user of the mobile phone. For example, a user of a mobile phone may be conducting a phone call at a baseball game with substantial ambient acoustic noise surrounding the event. The ambient acoustic noise surrounding the baseball game could include cheering fans, yelling vendors, and a public address system. The user's mobile phone includes active noise cancellation circuitry that senses the ambient acoustic noise through a microphone embedded in the mobile phone. The active noise cancellation circuitry generates an audio noise cancellation signal based on the sensed ambient acoustic noise. The active noise cancellation signal is played to the user through a speaker/earpiece of the mobile phone and negates or greatly reduces the perceived effect of the ambient acoustic noise to the user. Although active noise cancellation circuitry is effective in reducing effects of ambient acoustic noise on non-hearing impaired users, active noise cancellation circuitry often produces interference for hearing impaired users who use mobile phones with a hearing aid.
A hearing aid is typically worn by someone who suffers from hearing loss, and can compensate for the hearing impairment by amplifying the local sound field. Hearing aids operate in either a microphone (acoustic) mode or a telecoil (inductive) mode. In the microphone mode, sound waves that are incident upon a microphone which is integrated in the hearing aid are converted into an electrical audio signal. In the telecoil mode, an induction coil (also referred to as a telecoil or T-coil), which may also be inside the hearing aid, picks up the local magnetic field that has been modulated by the receiver or a dedicated coil of a nearby telephone handset. In both modes, the resultant electrical audio signal that has been picked up is subsequently processed, amplified and then converted to sound (by a small speaker inside the hearing aid) that can be heard by the user.
In telecoil mode, hearing aids typically turn-off their internal microphone and only receive audio that has been modulated by the receiver of a nearby telephone handset. Accordingly, the hearing impaired user would not be able to hear the ambient acoustic noise at the baseball game as the hearing aid is not picking up the ambient acoustic noise. Thus, the audio cancellation signal that is played to the user through a speaker/earpiece of the hearing aid would provide noise or interference to the hearing impaired user since there is no perceived ambient acoustic noise for the audio cancellation signal to reduce or negate.